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      Investigations of the Enzymes Involved in the Fructose Breakdown in the Cattle Lens

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          Abstract

          By introducing fructose into the glycolysis, it is possible to stimulate ATP formation. As is the case in animal experiments, in human lenses, too, the first step is the phosphorylation to fructose-1-phosphate via the enzyme ketohexokinase. The present investigation deals with the question whether enzymes present in the lens are responsible for the further steps in fructose degradation. Particularly the aldolase isoenzyme C splits fructose-1-phosphate into glyceraldehyde and dihydroxyacetone phosphate in the same way as in glucose catabolism. Dihydroxyacetone phosphate can further be directly degraded and thus utilized to ATP formation. From glyceraldehyde, glycerol (aldose reductase) or glycerate (aldehyde dehydrogenase) can be formed. The presence of triosekinase, which phosphorylates glyceraldehyde directly to glyceraldehyde-3-phosphate, could only be determined in the lens tissue of young animals. The presence of glycerokinase (glycerol → glycerophosphate) could not be verified. Thus, in the old lens tissue 1 ATP molecule net per fructose molecule can be formed. In older age, the glucose breakdown is limited by hexokinase and phosphofructokinase, so that the glucose, after transformation via the sorbitol pathway to fructose, can also be utilized for the energy metabolism.

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          Author and article information

          Journal
          ORE
          Ophthalmic Res
          10.1159/issn.0030-3747
          Ophthalmic Research
          S. Karger AG
          0030-3747
          1423-0259
          1982
          1982
          04 December 2009
          : 14
          : 3
          : 221-229
          Affiliations
          Klinisches Institut für experimentelle Ophthalmologie, Abteilung Biochemie des Auges, Universität Bonn, BRD
          Article
          265196 Ophthalmic Res 1982;14:221–229
          10.1159/000265196
          6285247
          57715c9b-965d-4cc7-a9a8-e58f093b710b
          © 1982 S. Karger AG, Basel

          Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

          History
          : 25 May 1981
          : 15 September 1981
          Page count
          Pages: 9
          Categories
          Original Paper

          Vision sciences,Ophthalmology & Optometry,Pathology
          Triosekinase,Bovine lens,Triosephosphate isomerase,Age dependence,Glycerol-3-phosphate dehydrogenase,Glycerokinase,Sorbitol pathway,D-Glycerate kinase,Energy metabolism,Aldehyde dehydrogenase,Carbohydrate breakdown

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